Overview & Objective: Research is needed to determine how planned CERP seepage control actions within the triple-porosity karstic Biscayne aquifer in the general area of Northeast Shark Slough will affect ground-water flows and recharge between the Everglades wetlands and Biscayne Bay. A fundamental problem in the simulation of karst ground-water flow and solute transport is how best to represent aquifer heterogeneity as defined by the spatial distribution of porosity, permeability, and storage. The triple porosity of the Biscayne aquifer is principally: (1) matrix of interparticle and separate-vug porosity, providing much of the storage and, under dynamic conditions, diffuse-carbonate flow; (2) touching-vug porosity creating stratiform ground-water flow passageways; and (3) less common conduit porosity composed mainly of bedding plane vugs, thin solution pipes, and cavernous vugs. The objectives of this project are to: (1) build on the Lake Belt area hydrogeologic framework (recently completed by the principal investigator), mainly using cyclostratigraphic and borehole geophysical methods to map porosity types and develop the triple-porosity karst framework between the Everglades wetlands and Biscayne Bay and (2) develop procedures for numerical simulation of ground-water flow within the Biscayne aquifer multi-porosity system. Technologies developed in this program are novel and will be applicable to integrated science approaches needed by decision makers for adaptive management of ecosystems.

Status: (1) Task 1: Drilled 10 test coreholes. (2) Task 2: Collected and processed geophysical logs for the 10 test coreholes. (3) Task 3: Interpretation of cyclostratigraphy and hydrostratigraphy and development of a new karst hydrgeologic framework for 10 coreholes between ENP and BNP partly completed. Produced 3-D computer-aided tomographic (CT) renderings of solid and porous portions of a very-highly permeable limestone sample that represents ichnofacies-dominated-porosity of the Biscayne aquifer from University of Texas-Austin CT- Imaging Laboratory. (4) Task 4: (a) The three-dimensional conceptual hydrogeologic model of Cunningham et al. (2006) for the karst Biscayne aquifer in the Lake Belt Area adjacent to northeastern ENP was converted into a numerical model using the Conduit Flow Process for MODFLOW-2005. (b) Cunnigham et al. (2006) data set also used in developmental experimentation with Biscayne Bay Model of Langevin (2001). (c) Initiated experiments at Florida International University-Department of Geological Sciences that will implement used of Lattice Boltzmann modeling to estimate hydraulic conductivity of a representative very-highly permeable ichnofacies-dominated-porous zone of the Biscayne aquifer.

Relevance to Greater Everglades Restoration Information Needs[See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]: This study supports several projects listed in the DOI science plan (specifically: Biscayne Bay Coastal Wetlands Project, L31N/L30 Seepage Management Pilot Project, Everglades National Park Seepage Management Project, Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project, Lake Belt In-Ground Reservoir Technology Pilot Project, and Landscape-Scale Science Needed to Support Multiple CERP Projects) by including development of procedures for numerical simulations of ground-water flow in the karst Biscayne aquifer from the Northeast Shark Slough area, where the CERPL31N/L30 Seepage Management Pilot Project and Everglades National Park Seepage Management Projects will alter current hydropatterns in ENP, and seepage to the east. The development of an expanded conceptual karst hydrogeologic framework planned in this proposal will be used to assist development of procedures for numeric simulations to improve the monitoring and assessment of the response of the ground-water system to hydrologic changes caused by seepage-management pilot project implementation. Specifically, the development of procedures for ground-water modeling of the karst Biscayne aquifer in the area of Northern Shark Slough will help determine the appropriate hydrologic response to rainfall and translate that information into appropriate performance targets for input into the design and operating rules to manage water levels and flow volumes for the two Seepage Management Areas. Mapping of the karstic stratiform ground-water flow passageways in the Biscayne aquifer is recent and limited to a small area of Miami-Dade County adjacent to the Everglades wetlands (Cunningham and others, 2006a,b). Extension of this karst framework between the Everglades wetlands and coastal Biscayne Bay will aid in the simulation of coupled ground-water and surface-water flows to Biscayne Bay. The development of procedures for modeling in the karst Biscayne aquifer will useful to the establishment of minimum flows and levels to the bay and seasonal flow patterns. Also, these improved procedures for simulations will assist in ecologic modeling efforts of Biscayne Bay coastal estuaries.

Key Findings:

Analysis of corehole data from the Lake Belt area suggests that much of the ground-water flow in this area is related to biogenic touching-vug porosity that forms tabular-shaped stratiform flow zones. Biogenic porosity and its hydrologic importance were determined by examining outcrops, cores, and borehole geophysical data that include digital optical image logs and flowmeter, fluid conductivity, and fluid temperature measurements.

Digital image logs and 72 of 85 geophysical measurements (85%) in 21 boreholes indicate that biogenic porosity is the principal pore type in ground-water flow zones. All the remaining borehole geophysical measurements across ground-water flow zones detected inflow or outflow from bedding plane vugs, with the exception of a single cavern-sized vug.

Biogenic porosity in the Biscayne aquifer is related to predictable vertical positions in stratigraphic cycles and much of it can be mapped reliably.

Computer-aided tomographic 3-D rendering of a highly-permeable ground-water flow zone has been successful and will be used in future flow simulations using Lattice-Boltzmann modeling to estimate hydraulic conductivity at various Reynolds numbers.

The diffuse and preferential flow zones of the Biscayne aquifer (Cunningham et al. 2006) were converted into a numerical model using the Conduit Flow Process (CFP) for MODFLOW-2005.